A quantitative study of the extent and duration of regenerative sprouting induced by crush of the optic nerve in goldfish is being completed. The number of regenerative sprouts in the nerve distal to the crush increases by a factor of 4 during the first 3 post-operative months and then returns toward normal. This return is accompanied by an increase in percent of axons which are myelinated. The time course of recovery of normal optic axon number and morphology does not parallel the return of visual function although it does relate to the return of synaptic density in the tectum. Regenerating axons are closely associated with glial cell cytoplasm during the outgrowth period. A quantitative study of reinnervation of the optic tectum indicates that retinal axons normally make about 40% of the terminals in the SFGS, that these terminals are for the most part small, make asymmetric contacts on small dendrites, contain round vesicles and are not morphologically distinguishable from many other SFGS terminals. Following optic nerve crush, this population of terminals decreases. Large numbers of regenerating axons enter the tectum at 1 month but normal synaptic density is not achieved for several months. This indicates that selection of appropriate post synaptic sites or synaptogenesis is the time limiting factor rather than axonal growth.